Australian-Israeli who apparently hanged himself in Ayalon prison had angrily denied involvement in Israeli espionage.

Multiple Australian media outlets are reporting that Ben Zygier, named Tuesday as an Australian-born Mossad agent who died apparently by his own hand in an Israeli high-security jail, had been under investigation in his native land at the time of his death.

Australia's ABC News on Tuesday named was Melbourne native Zygier as “Prisoner X”, saying he had been jailed for unknown reasons in early 2010, a decade after he moved to Israel and years after he being recruited by Mossad. The report also said that Zygier's detention has been one of the most closely-guarded secrets in Israel in recent years, one that the Israeli government had tried relentlessly to cover up.

According Fairfax Media, which owns the Sydney Morning Herald, the Australian Security Intelligence Organisation suspected Zygier of using his Australian passport in order to conduct espionage for Israel.

The Herald said Wednesday that in early 2010, a Fairfax Media reporter had confronted Zygier, who was known in Israel as Ben Alon, about his activities for Mossad. Zygier had angrily denied the allegations, the report said, calling them "total bulls**t." By late 2010, Zygier had apparently hanged himself in his cell at Ayalon high-security prison.

In February 2010, the Age news organization named Zygier as one of three Australian-Israelis who were using their foreign nationality as a "cover" for espionage activity.

According to the report in the Age, the investigation predates the assasination of Mahmoud al-Mabhouh, the Hamas operative killed in Dubai in January 2010 in what is widely believed to be a Mossad hit. Israel drew intense criticism from Australia and Britain for the suspected use of their passports in the operation. Zygier and his two fellow Australians were not suspected in the Mabhouh operation, the report said.